The present invention relates to a remote control switch device which remotely operates a power load switch device by using a low voltage signal communication line and displays the operational position of the power load switch device at the side from which it is operated.
For remotely controlling a power load circuit such as an illumination lamp, it is desired that the operating circuit therefor be safe, easily operable and that no current constantly flow therethrough. For this purpose, in remotely controlling a simple load which may be operated merely by opening or closing a main switch such as a lamp load, there has recently been used as a main switch a mechanical holding type relay, which is hereinafter termed a "keep relay", which alternatively repeats opening and closing operations simply by momentarily passing an electric current through an electromagnetic coil thereof with the relay being consequently retained mechanically at the opened or closed position thereby set.
When such a keep relay is employed, the operating circuit may safely be insulated through an isolating transformer from a main circuit. Further, a long wire to a remote circuit may be provided as a small and lightly-insulated signal communication line because it need carry only a low level current. Since with this keep relay, however, a main switch is opened or closed merely by momentarily passing an electric current through a single electromagnetic coil, it cannot be set to a desired state from the position from which it is operated unless it is known whether or not the switch is presently opened or closed at the position from which the switch is operated. Therefore, an indicator lamp is provided at the operating position to indicate the opened or closed state of the main switch. Remote control switch devices of this type recently have employed an energy-saving type of indicator lamp, but the circuit therefor is complicated. Moreover, most remote control switch devices require more than three wires to connect it to the operating circuit.
FIG. 1 is a wiring diagram showing an example of a conventional remote control switch device in which the aforementioned disadvantages have been eliminated. In FIG. 1, a main switch 3 coupled between an a-c power supply 1 and a load 2 is a contact of a keep relay. The keep relay also includes a switching type auxiliary contact 4 interlocking with the main switch 3 and an electromagnetic coil 5. Two diodes 6a and 6b, connected in opposite directions, have first terminals connected to one end of the coil 5 of the keep relay in a control circuit 7 with the second terminals thereof connected through the auxiliary contact 4 so as to switch the connections of the diodes. An operation indicating circuit 8 includes a parallel connection of a series circuit of an indicator lamp 9 and a diode 10 and of a series circuit of a change-over switch 11 and two diodes 12a and 12b with first terminals connected in opposite directions to the switch 11 and with second terminals connected to signal communication lines 13. An isolating transformer 14 has an input winding connected to the power supply 1, one terminal of a secondary winding connected directly to the electromagnetic coil 5 and the other terminal of the secondary winding connected via the signal communication lines 13 through the operation indicating circuit 8 to the armature of the auxiliary contact 4.
When the switch 11 in the operation indicating circuit 8 is switched to connect the diode 12a, and electric current flows in a circuit composed of the diode 12a, the switch 11, the transformer 14, the electromagnetic coil 5, the diode 6a, and the auxiliary contact 4 (as designated by solid-line arrows) to thereby energize the electromagnetic coil and to thus operate the keep relay. Thereby, the main switch 3 is closed, and the load 2 is connected to the power supply 1. When the auxiliary contact 4 is switched to connect the diode 6b, the electric current flowing in the circuit (as designated by solid-line arrows) is interrupted and an electric current flows in a circuit composed of the diode 6b, the electromagnetic coil 5, the transformer 14, the indicator lamp 9, the diode 10, and the auxiliary contact 4 (as designated by broken-line arrows) to thereby turn on the lamp 9 to indicate that the load 2 is connected to the power supply 1. Then, the switch 11 is returned to its intermediate position. In this state, an electric current still flows through the electromagnetic coil 5 since the indicator lamp 9 is connected in the circuit. However, this current is very low and can thus be ignored so far as the coil 5 is concerned.
When the switch 11 in the operation indicating circuit 8 is switched to connect the diode 12b, an electric current flows in a circuit (as designated by broken-line arrows) except for the indicator lamp 9 and the diode 10 to thereby again energize the electromagnetic coil 5 so as to operate the keep relay. This opens the main switch 3 and the current flow to the load 2 is interrupted. Inasmuch as the auxiliary contact 4 is simultaneously switched to connect the diode 6a, even if the switch 11 is returned to the intermediate no-connection position, no electric current will flow through the indicator lamp 9. That is, the indicator lamp 9 will not then turn on, thus indicating the disconnection of the load 2 from the power supply 1.
Although the conventional remote control switch device can thus be operated merely by momentarily passing an electric current through an isolating transformer using two signal communication lines, a change-over switch must also be provided which is complicated in operation. Further, when the indication lamp is turned on, a current flows through the electromagnetic coil of the keep relay. In case that the number of the indicator lamps is small, the magnitude of this current flowing through the coil will be acceptably small and can be ignored. However, in case that a large number of operating circuits is required for operating the main switches from the respective operating circuits, a corresponding larger number of indicator lamps must be employed and a larger magnitude of current will flow in the coil. The increased magnitude of the current may eventually cause an erroneous operation of the keep relay.
FIG. 2 shows another example of a conventional remote control switch device and employing a keep relay. In FIG. 2, a main switch 23 inserted between an a-c power supply 21 and a load 22 includes a main contact 24, a keep relay 27 including a switching type auxiliary contact 25 interlocking with the main contact 24 and operating simultaneously upon operation of the main contact 24 and an electromagnetic coil 26, and diodes 28a and 28b connected in opposite directions and coupled to be switched by the auxiliary contact 25 connected in series with the electromagnetic coil 26. The input or primary winding of an isolating trnsformer 29 is connected to the power supply 21 and the secondary winding thereof is connected as a control power supply to a main switch 33 through signal communication lines 35 through a remotely-located operation indicating circuit 30. The operation indicating circuit 30 includes a keep relay 38 including a switching contact 37 and an electromagnetic coil 36 for actuating the contact 37, a switching type push-button switch 33, diodes 34a and 34b connected in opposite directions and switched in connection by the switching contact 37, and an indicator lamp 31. The connection of the diodes 34a and 34b to the electromagnetic coil 36 is switched by the push-button switch 33. The keep relay 38 used in the operation indicating circuit 30 may be of a small capacity type and need be capable only of switching the contact 37. The impedance of the coil 36 is thus very high compared with that of the coil 26.
When the push-button in the operation indicating circuit 30 is depressed, the switch 33 is switched from the position shown in FIG. 2 to connect with the armature of the switching contact 37, and an electric current flows in a circuit composed of the push-button switch 33, the transformer 29, the coil 26, the diode 28a, the auxiliary contact 25, the diode 34a, and the switching contact 37 (as designated by solid-line arrows) thereby energizing the electromagnetic coil 26. Thus, the keep relay 27 is operated to close the main contact 24 and the load 22 is connected to the power supply 21. The auxiliary contact 25 is simultaneously switched at that time, and current flowing along the path designated by soid-line arrows is interrupted. Then, a current flows in a circuit composed of the auxiliary contact 25, the diode 28b, the coil 26, the transformer 39, the indicator lamp 31, and the diode 34b (as designated by broken-line arrows) thereby turning on the lamp 31 to indicate that the load 22 is connected to the power supply 21. Since the impedance of the indicator lamp 31 is very high as compared with that of the electromagnetic coil 26, the keep relay 27 will not be operated by the current then flowing therethrough. When the push-button is released, the switch 33 is returned to the side of the electromagnetic coil 36 to connect the coil 36. Then, a current flows in a circuit composed of the coil 36, the auxiliary contact 25, the diode 28b, the coil 26, and the transformer 29 (as designated by broken-line arrows) to thereby energize the coil 36. Thus, the keep relay 38 is operated to switch the contact 37.
The electromagnetic coils 36 and 26 are connected in series with each other at this time. However, since the impedance of the electromagnetic coil 36 is very high as compared with that of the electromagnetic coil 26 even if the coil 36 is always energized, the coil 36 will not burn out and the keep relay 27 will not operate.
When the push-button in the operation indicating circuit 30 is again depressed, the respective switches are switched to positions opposite to those shown in FIG. 2 and current accordingly flows in a circuit composed of the push-button switch 33, the switching contact 37, the diode 34b, the auxiliary contact 25, the diode 38b, the coil 25, and the transformer 29 (as designated by broke-line arrows) to thereby energize the coil 26. Accordingly, the keep relay 27 is operated opening the main contact 24 and interrupting the load 22 from the power supply 21. Since the auxiliary contact 25 is simultaneously switched, the current flowing in the direction designated by the broken-line arrows is interrupted and the indicatior lamp 31 is consequently deenergized. When the push-button is released, the switch 33 is returned to the original state as shown in FIG. 2, and current accordingly flows in a circuit composed of the push-button switch 33, the transformer 29, the coil 26, the diode 28a, the auxiliary contact 25, and the coil 36 (as designated by solid-line arrows). Thus, the keep relay 38 is operated to switch the contact 37, and all the contacts are switched to the positions shown in FIG. 2.
As heretofore described. the conventional remote control switch device can operate with two signal communication lines using an isolating transformer. However, the switches in the operating circuit employ relatively complicated and expensive keep relays. There has been also proposed a remote control switch which controls a main circuit using a simple push-button switch without a keep relay. This switch is nonetheless disadvantageous in that it incorporates an operation indicating circuit used exclusively for the push-button and which cannot therefore be conveniently interchanged with or commonly used as an operation indicating circuit with a keep relay of the type previously described.